Method and apparatus for assigning spectrum of a wireless local area network

ABSTRACT

One embodiment of the invention includes assigning channels to a set of access points coupled to a network. The network includes a set of wireless network nodes. Each access point communicates, using one of the channels, to a subset of the wireless network nodes. Each channel corresponds to a different frequency range in the electromagnetic spectrum. The embodiment includes the following steps. At least a first access point of the set of access points transmits a plurality of messages. A measure of interference between access points communicating on a first channel is determined from the plurality of messages. A second set of channel assignments, that results in a lower amount of interference between access points communicating on the first channel, is determined. The second set of channel assignments is assigned to the set of access points. Thus, non-interfering frequency assignments for the access points can be determined.

THE BACKGROUND OF THE INVENTION

1. The Field of the Invention

This invention relates to the field of wireless local area networks(LANs). In particular, the invention relates to assigning spectrum toaccess points in a wireless LAN.

2. A Description of the Related Art

Computer networks supply data and services to the computers and devicesconnected to the network. Traditionally, the connection to the networkhas been through a wired medium such as coaxial cable, fiber optics,twisted pair, etc. However, there are a number of applications thatbenefit from a completely, or partially, mobile computer (or otherdevice). Such computers connect to the network using wirelesscommunications. Wireless communications rely on data transfers usingradio transmitters and receivers.

A wireless LAN includes access points and wireless network nodes. Theaccess points connect wireless network nodes to the wired part of theLAN or to some other wireless part of the LAN. An access pointcommunicates, using wireless communications, with the wireless networknodes in that access point's communications area. Thus, an access pointmaintains a number of simultaneous wireless communications links with anumber of wireless network nodes. The access points and the wirelessnetwork nodes include transceivers (transmitters and receivers) toestablish and maintain the wireless communications links. Thetransceivers transmit and receive signals in the electromagneticspectrum, for example, in the infrared spectrum, at 902 MHz or at 2.4GHz.

The access points typically support multiple channels. This allows twoor more access points, communicating on different channels, to haveoverlapping coverage areas. Different channels can be supported byaccess points in different ways. For example, Proxim, Inc. supplies awireless LAN product line called RangeLAN2™. The RangeLAN2 usesfrequency hopping spread spectrum communications. A RangeLAN2transmitter hops from frequency to frequency while transmitting to areceiver. Different channels are supported by different, orthogonal,hopping sequences. Another technique is called direct sequence spreadspectrum (DSSS) communications. DSSS breaks the electromagnetic spectruminto a number of sub-bands. Each sub-band corresponds to a differentchannel.

One of the problems with DSSS communications, or any communicationstechnique where a channel corresponds to a specific part of spectrum, isthat access points with overlapping coverage areas need to be assignedto different channels. If access points with overlapping coverage areasare not assigned to different channels, then the transmissions willinterfere with each other. This leads to a need to assign differentchannels to the access points that have overlapping coverage areas.

To adjust for changes in the wireless communications environment, newaccess points may be added or access points may need to be moved. Thismay change the overlapping areas of the access points, possibly causingsome access points to interfere with other access points. Thus, what isneeded is a method and apparatus for displaying the amount ofinterference between access points and for generating a new set ofchannel assignments for the access points that will reduce, oreliminate, the interference of the access points.

A SUMMARY OF THE INVENTION

A method and apparatus for maintaining non-interfering frequencyassignments of wireless-based computer networking products is described.

One embodiment of the invention includes assigning channels to a set ofaccess points coupled to a network. The network includes a set ofwireless network nodes. Each access point communicates, using one of thechannels, to a subset of the wireless network nodes. Each channelcorresponds to a different frequency range in the electromagneticspectrum. The embodiment includes the following steps. At least a firstaccess point of the set of access points transmits a plurality ofmessages. A measure of interference between access points communicatingon a first channel is determined from the plurality of messages. Asecond set of channel assignments, that results in a lower amount ofinterference between access points communicating on the first channel,is determined. The second set of channel assignments is assigned to theset of access points. Thus, non-interfering frequency assignments forthe access points can be determined.

In one embodiment, each access points transmits a message requesting allthe access points that detect the message to reply. Each access pointmeasures the strengths of the reply messages to determine the radioproximity of that access point's neighbors. The reply messages indicateto what degree other access points are directly interfering with a givenaccess point's wireless communications, by communicating on the samechannel as that access point. The reply messages also indicate whichneighbors are transmitting on channels that are near the channel beingused by an access point. The reply messages also indicate whichneighbors can be detected by an access point but are assigned tochannels that neither directly or nearly interfere. In one embodiment,the radio proximity information is tabulated by a network manager. Thetable indicates to what degree each access point is directly conflictingwith any neighboring access points, given that access point's presentchannel assignment. The table also indicates near conflicts (neighborscommunicating on near channels) and other signals detected for eachaccess point.

In one embodiment, the radio proximity information is processed toreduce or eliminate direct conflicts and near conflicts; thereby,significantly improving the wireless communications of the network. Inone embodiment, an iterative process is used to find better channelassignments by comparing any possible new channel assignments with theprevious best (lowest amount of direct and/or near conflict) channelassignments.

In one embodiment, the new channel assignments are then displayed to theuser with the radio proximities shown graphically. The user can thenchange any of these new assignments before the new assignments aretransmitted to the access points.

Although many details have been included in the description and thefigures, the invention is defined by the scope of the claims. Onlylimitations found in those claims apply to the invention.

A BRIEF DESCRIPTION OF THE DRAWINGS

The figures illustrate the invention by way of example, and notlimitation. Like references indicate similar elements.

FIG. 1 illustrates a wireless local area network (LAN) determining thechannel assignments for the access points in the LAN.

FIG. 2 illustrates determining and assigning a new set of channelassignments for the access points in the LAN of FIG. 1.

FIG. 3 illustrates the tables used to generate the new set of channelassignments.

FIG. 4 illustrates a graphical user interface for displaying the levelsof conflict between access points and for allowing a user to reassignchannel assignments.

THE DESCRIPTION

A Wireless LAN

FIG. 1 illustrates a wireless local area network (LAN) determining thechannel assignments for the access points in the LAN. The LAN of FIG. 1is illustrative only and is not the only network in which one embodimentof the invention operates.

The wired network 100 includes: a wired media; a number of wirelessaccess points (an access point 1 111, an access point 2 112, an accesspoint 3 113 and an access point 4 114); and, a network manager 110. Thewired media includes one or more of coaxial cable, twisted pair, fiberoptics, and any other media that support wired communications. In oneembodiment, the wired media is replaced by a wireless communicationsnetwork (e.g., RangeLINK™ from Proxim, Inc.). The access pointscommunicate with the network manager 110 over the wired media.

The network manager 110 includes a computer such as an IBM compatiblePC, a Sun workstation, a Macintosh computer, or a specialized networkmanagement device. In any case, the network manager 110 includes amemory for storing information and a process for accessing theinformation and manipulating the information.

The access points communicate with a number of wireless network nodes(e.g., a network node 101, a network node 102, and a network node 103).Each access point and each wireless network node includes a transceiver.Each transceiver supports wireless communications. One embodiment of theaccess point 2 112 is described in the U.S. patent application Ser. No.08/394,378, filed Feb. 24, 1995.

Each access point communicates with its set of wireless network nodesusing a specific channel. In the example of FIG. 1, the access point 2112 uses channel three, the access point 1 111 also uses channel three,the access point 3 113 uses channel four, and the access point 4 114uses channel seven.

The following discussion relates to how the access point 2 112communicates with the network node 101, the network node 102 and thenetwork node 103. However, this discussion applies to any of the accesspoints and any wireless network node. Importantly, the access point 2112 communicates with the network node 101, the network node 102 and thenetwork node 103, using a single channel (channel three). The channelcorresponds to a specific portion of the electromagnetic spectrum. Inthis example, the access point 1 111 is also communicating on channelthree. As the network node 103 can detect messages from both the accesspoint 1 111 and the access point 2 112, the messages interfere with eachother. The interference is undesirable.

When a new access point is added to the wireless network, an accesspoint is moved, or a source of interference jams or degrades the qualityof the communications from the access point to the wireless networknodes, one or more access points may have to change their channel. Forexample, in FIG. 1, assume that access point 1 111 has been added to thenetwork and that an interference source 120 has begun jamming thecommunications channel used by the access point 2 112. Also assume thatthe same channel is being used by the access point 1 111 and the accesspoint 2 112. One embodiment of the invention detects the interferencebetween the two access points, notes the existence of the jamming fromthe interference source 120, and generates a new set of channelassignments for the access points that reduces the communicationsconflict due to the interference between the two access points and thejamming. The communications conflict includes a measure of the radioproximity of access points that communicate on the same, or a near,channel.

As noted, the invention also attempts to generate a set of channelassignments that reduces the amount of near conflict between two or moreaccess points. A near conflict occurs when overlapping access points usechannels that are near to each other in the electromagnetic spectrum.For example, if the access point 1 111 uses channel three, out of elevenpossible channels, and the access point 2 112 uses channel four, thenthese two access points are said to be using two channels near eachother. For better wireless communications performance, it is desirableto have the access points, in close radio proximity, use channels thatare further apart than a single channel. For example, it is moredesirable that access point 2 112 use channel one or some other channelfurther away from channel three in the electromagnetic spectrum.

Generally, to generate a new set of channel assignments, one embodimentof the invention first determines the amount of communications conflictwith other sources for each of the access points for their presentchannels. The amount of communications conflict indicates the amount ofinterference, from other radio transmitters, experienced by a givenaccess point for a given channel. Next, the amount of communicationsconflict for all the access points is tabulated. If possible, a new setof channel assignments is generated that results in a reduced amount ofcommunications conflict. Finally, the new set of channel assignments areprovided to the access points so that they can switch channels. Thus,changes in the wireless communications environment can be compensatedfor by one embodiment of the invention.

One of the first steps in determining the amount of communicationsconflict is to learn the neighbor access points for each access point.Each access point transmits a "Where are you" message 150 on eachchannel. The message 150 includes an identifier (e.g., a network addressof the access point, or some unique identifier) of the transmittingaccess point. For example, the access point 1 111 transmits the message150 on each channel.

In one embodiment, the message 150 is transmitted at a higher power thannormal transmissions to the wireless network nodes. This is because itis possible that two access points cannot normally detect each other'spresence at nominal signal output levels, but that a wireless networknode, positioned to communicate with both access points, may be able todetect signals from both of those nodes. The message 150 includes anidentifier identifying the source of the message 150.

The access points that detect the message 150 then reply with an "I amhere" message (e.g., the access point 2 112 detected the message 150 andresponds with an "I am here" message 162; similarly a message 163 and amessage 164 are transmitted by the access point 3 113 and the accesspoint 4 114, respectively). The "I am here" message includes anidentifier (e.g., a network address, or some unique identifier) of thetransmitting access point of the "I am here" message. The "I am here"message is transmitted on the channel used to receive the "Where areyou" message. Optionally, the "I am here" messages are sent at theincreased power level. This helps ensure that transmitting access pointof the "Where are you" message receives the "I am here" messages.

The transmitting access point of the "Where are you" message measuresthe received signal strength of the "I am here" messages. Thus, eachaccess point learns the signal strength of its neighbors.

Optionally, each access point includes a device for detectinginterference on one or more channels. Each access point then alsoincludes an amount of interference for each channel.

The network manager 110 collects the received signal strengthsinformation to determine the amount of communications conflict among theaccess points using their present channel assignments. The networkmanager 110 then generates a set of new channel assignments that resultsin a reduced amount of communications conflict among the access points.In the example of FIG. 1, for the new channel assignments, the accesspoint 2 112 is assigned channel one, the access point 1 111 keepschannel three, the access point 3 113 is assigned channel five, and theaccess point 4 114 keeps channel seven. The network node 103 can nowcommunicate with the access point 2 112 without interference from theaccess point 1 111.

In one embodiment, the network manager 110 generates the set of newchannel assignments so that only a few access points need change theirchannels. By minimizing the number of access points that need changetheir channel, any disruptions of communications between the accesspoints and the wireless network nodes are minimized.

New Channel Assignments

FIG. 2 illustrates determining and assigning a new set of channelassignments for the access points in the LAN of FIG. 1. Firstinformation is obtained about the neighboring access points and then thenew set of channel assignments is generated and broadcast. Step 210through step 216 ensure that each access point transmits a "Where areyou" message 150 and measures the signal strength of any received "I amhere" messages. At step 210, a test is made to determine whether eachaccess point in the LAN has sent the "Where are you" messages. In oneembodiment, the network manager 110 sends a message to each accesspoint, in turn, to execute step 212 through step 216. The networkmanager 110 then performs step 220 through step 260.

In one embodiment, prior to transmitting the "Where are you" messages150, an access point halts communications with its wireless networknodes. This is because the "Where are you" messages 150 are transmittedfor each channel. As the network nodes are communicating with the accesspoint on a specific channel, and the access point needs to transmitmessages on different channels, if the communications were not halted,the network nodes would lose contact with the access point as itswitched channels.

At step 212, a given access point transmits a "Where are you" message150 on a first channel. As noted above, the "Where are you" message 150includes an identifier identifying the transmitting access point. Forexample, the message 150 from the access point 1 111 includes theaddress of the access point 1 111. Step 212 is executed for each channelfor each access point.

In response to the "Where are you" message 150, any neighbor accesspoints that detect the message, respond with their own "I am here"message. For example, assume that the access point 1 111 transmits a"Where are you" message 150 on channel three and only the access point 2112 is communicating on channel three, then only the access point 2 112will transmit an "I am here" message (assuming that the access point 2112 detected the "Where are you" message 150). While looping throughstep 210 through step 216, step 212 is executed for each channel for theaccess point 1 111, resulting in three "I am here" messages 162, 163 and164 being sent by the other access points.

At step 214 and step 216, the given access point receives and processesany "I am here" messages from any neighbor access points. At step 214, atest is made to ensure that all the received "I am here" messages areprocessed in response to a given "Where are you" message 150 on a givenchannel. In one embodiment, an access point uses a timeout to determineif all of the "I am here" messages have been received. For example, whenthe access point 1 111 transmits the "Where are you" message 150, theaccess point 1 111 starts a counter. The access point 1 111 then beginsprocessing any received "I am here" messages. The access point 1 111then stops listening for "I am here" messages when the counter reaches apredetermined value (e.g., after thirty seconds).

At step 216, the transmitting access point of the "Where are you"message 150 tests the received signal strength of the "I am here"messages on the given channel. The access point then saves the receivedsignal strength, and the identifier of the sender of the "I am here"message, for each received "I am here" message. In one embodiment, theaccess point also saves the channel used by the sender of the "I amhere" message. Each access point maintains a local neighbors table thatholds this information.

For example, as step 214 and step 216 are executed, during the step 210through step 216 loop for each channel for the access point 1 111, thefollowing information is stored by the access point 1 111: access point2 112 detected at signal strength eight on channel three; access point 3113 detected at signal strength two on channel four, and access point 4114 detected at signal strength five on channel seven.

Optionally, before, or after step 212, a step can be included fordetecting any interference from outside sources for a given channel of agiven access point. For example, if the access point 2 112 detectsinterference on channels one through five as a result of theinterference source 120, then this information is also stored by theaccess point 2 112. During the generating of the new channelassignments, these jammed channels will be excluded as possible channelsfor the access point 2 112.

After step 210 through step 216 have been completed for each channel foreach access point, then step 220 through step 260 are performed. At step220, a conflict level table (or conflict table) is generated from allthe local neighbors tables. The conflict table defines, for each accesspoint, the present channel used, the amount of direct conflict, theamount of near conflict and the amount of the other signals detected.The amount of direct conflict corresponds to the total signal strengthof "I am here" messages received by an access point on the presentchannel of that access point. The amount of near conflict corresponds tothe total signal strength of "I am here" messages received by an accesspoint on channels near to that access point's present channel. Theamount of other signals detected corresponds to the total signalstrength of "I am here" messages received by an access point on channelsthat are neither the present channel nor the near channels.

In one embodiment, before determining the total received signalstrength, an average detected signal strength is first determined. Theaverage detected signal strength corresponds to the average of thereceived signal strength of a first message from a first access point toa second access point and the received signal strength of a secondmessage from the second access point to the first access point. Forexample, if the access point 1 111 receives the "I am here" message 162,from access point 2 112, at a signal strength of eight, and the accesspoint 2 112 receives an "I am here" message, from access point 1 111, ata signal strength of nine, then the average detected signal strength iseight and one half.

At step 230, a new (or recommended) set of channel assignments aregenerated from the conflict table. The new set of channel assignmentsresults in a lower amount of conflict in the conflict table. In somecases, a new set of channel assignments that result in a lower amount ofconflict may not exist. In such cases, the network administrator (LANadministrator, or some other user) is notified of this fact.

A number of techniques are used in step 230 to determine an alternativeset of channel assignments. For example, in one embodiment, the conflicttable is sorted, first on direct conflict values, then on near conflictvalues. Next, the access point with the highest conflict value isassigned to a different channel. The conflict table is then recomputedto determine whether the new channel assignment results in no directconflict for the access point. If not, then a different channel isselected for the access point. The above steps are repeated until achannel assignment for the access point is found that results in nodirect conflict. The new table is then resorted and the above steps arerepeated until all the access points have zero direct conflict values.In one embodiment, the above steps are repeated until the access pointshave a minimal amount of direct conflict. In one embodiment, after thedirect conflicts are reduced, the channel assignments are altered toresult in a lower amount of near conflict. In one embodiment, thechannel assignments are altered to result in as few channelreassignments as possible while still eliminating all of the directconflicts.

In one embodiment, a number of conflict tables are created. Eachconflict table includes only those access points that are within radioproximity (i.e., have a non-zero value for the direct conflict, nearconflict or other signal detection) of at least one other access pointin the table. Each table is then processed separately to generate a newset of channel assignments for the access points in that table.Generating a number of conflict tables can greatly reduce the number ofcalculations that need to be performed to generate the new channelassignments. This is because determining the new channel assignmentsbecomes significantly more difficult for each additional access point ina table (i.e. the new channel assignments problem is greater than O(n)).

In one embodiment, the step 230 only generates a set of new channelassignments that results in no direct conflicts. This reduces the numberof access points that will have to change their channel, thus, reducingthe number of wireless network nodes that will have to change theirchannels and thereby reducing the impact on the network's performance.

If the interference sources are also included in the new channelassignment generation process, then a set of available channels is firstdetermined for each access point. The set of available channelsrepresents all the channels that are not being jammed by an interferencesource 120 for a given access point. Note, that in one embodiment, theLAN administrator can identify a set of unusable channels for an accesspoint. This is particularly useful where the interference source 120 isintermittent. For example, if the interference source 120 was amicrowave oven that jams channels three through five of the access point1 111, then the LAN administrator can set the unusable channels for theaccess point 1 111 to be channels three through five.

At step 240, the conflict level information, from the conflict table, isdisplayed. In one embodiment, the conflict level information isdisplayed on the network manager's 110 display as shown in FIG. 4.

At step 250, the network administrator can modify the new channelassignments. This provides the network administrator with flexibility. Anetwork administrator may wish a particular access point to be assignedto a particular channel, may know that a new access point will be addedto the network and/or may want to reserve a channel for that accesspoint, or for some other reason change the new channel assignments.

At step 260, the network manager 110 sends the new channel assignmentsto the access points. The access points that have new channels thentransmit the new channel to their wireless network nodes. The wirelessnetwork nodes and the access points then begin communicating on the newchannels. Optionally, step 240 and step 250 are not performed, resultingin an automatic reassignment of the channels.

As an alternative to the above method, rather than measuring the signalstrength of the received "I am here" messages, each access pointmeasures the received strength of the "Where are you" messages 150. Aconflict table is generated from this information. This results in areduced number of messages that need be sent because "I am here"messages are not transmitted.

As another alternative to the above method, the neighbor tableinformation is not stored in the access points. Each time an "I am here"message (or a "Where are you" message 150) is received at an accesspoint, that access point transmits the message sender's identifier, themessage receiver's identifier, the received signal strength and thechannel to the network manager 110, or back to the sender access point,over the wired network 100. The network manager 110 then builds theconflict level table from all of these messages, or the access pointgenerates a local neighbors table. Transmitting the information to thenetwork manager has the advantage of reducing the computing power andthe memory requirements of the access points.

In one embodiment, the network administrator can select a subset of allthe access points in which to apply the method of FIG. 2. This featureprovides the network administrator with added flexibility in managingthe network. For example, assume that the access points of FIG. 1 arebut a small number of the access points in the wired network 100, butthat the access points of FIG. 1 are physically located far from theother access points. In this case, the network administrator canindicate that only a select few of the access points should be evaluatedfor new channel assignments.

The method of FIG. 2 can be performed anytime the wirelesscommunications environment changes. The method can also be executed on aregular basis, for example, once a week, or daily.

Conflict Table Creation and Use

FIG. 3 illustrates the tables used to generate the new set of channelassignments. The table format is illustrative of how the informationfrom the access points can be represented but is not the only way ofstoring and organizing the information. For example, the informationcould be stored and organized as graphs, linked lists, or arrays. Eachaccess point includes a local neighbor table. The local neighbor tablesare generated from the step 210 up to the step 220. The access point 2112 includes the local neighbor table 312. The access point 1 111includes the local neighbor table 311. The access point 3 113 includesthe local neighbor table 313. The access point 4 114 includes the localneighbor table 314.

Each local neighbor table includes the strength of any "I am here"messages, the identifier for the access point that transmitted the "I amhere" message, and the channel upon which that message was received. Forexample, the local neighbor table 311 includes the following entries:for the access point 2 112, an "I am here" message 162 was received onchannel three with a strength of eight; for the access point 3 113, an"I am here" message 163 was received on channel four with a strength oftwo; and for the access point 4 114, an "I am here" message 164 wasreceived on channel seven with a strength of five. The following tablelists the values of the received signal strengths, the channels and theaccess points.

                  TABLE 1    ______________________________________    Access     Access     Access     Access    Point 1 111               Point 2 112                          Point 3 113                                     Point 4 114    AP     Signal  AP     Signal                                AP   Signal                                           AP   Signal    #      Strength                   #      Strength                                #    Strength                                           #    Strength    ______________________________________    1 (3)  X       1 (3)  9     1 (3)                                     2     1 (3)                                                4    2 (3)  8       2 (3)  X     2 (3)                                     4     2 (3)                                                0    3 (4)  2       3 (4)  4     3 (4)                                     X     3 (4)                                                9    4 (7)  5       4 (7)  0     4 (7)                                     9     4 (7)                                                X    ______________________________________

The channel is shown in parenthesis next to the access point identifier.The signal strength is shown on a relative scale from one to ten (tenbeing the maximum). For the purposes of illustration, an entry is shownfor a message with a zero signal strength in the local neighbor tablesfor the access point 2 112 and the access point 4 114. In oneembodiment, a zero signal strength means that no "I am here" message wasdetected by the access point. Therefore, the entry would not normally beincluded in that local neighbor tables.

From the local neighbor tables, the network manager 110 generates theconflict level table 370. The conflict level table 370 includes thetotal amount of direct conflict, near conflict and other signalsreceived by an access point. Using the local neighbor tables above, theamount of direct conflict is 8.5 for the access point 1 111. This is thetotal signal strength of all the detected signals at the access point 1111 from all the sources transmitting on the same channel as the accesspoint 1 111 (e.g., access point 2 112 with a value of eight); and thedetected signals at the other access points (e.g., access point 2 112with a value of nine) from all the receivers of "I am here" messagesfrom the access point 1 111 that are also using the same channel as theaccess point 1 111. Similar calculations are made for the other entriesin the conflict level table 370.

After using the process of step 230, a new set of channel assignments isgenerated. In the example of FIG. 3, the reduced conflict level table372 corresponds to the new channel assignments. Note that both thedirect conflicts and the near conflicts have also been reduced to zero.Also note that only two access points need change their channels, thus,a relatively small disruption of the wireless communications networkwill occur.

Graphical User Interface

FIG. 4 illustrates a graphical user interface for displaying the levelsof conflict between access points and for allowing a user to reassignchannel assignments. In one embodiment, the network manager 110 displaysthe channel assignment display 400 in a window based user interface. Thegraphical user interface shown is an example of the type of interfacethat is presented to the user during the channel reassignment process.In another embodiment, the graphical user interface graphically showsthe physical locations of the access points (e.g., as part of floorplan).

The channel assignment display 400 includes a number of graphicalelements that help communicate the present status of the wireless LAN.Each graphical element includes text and/or an icon and/or some othergraphics. The channel assignment display 400 includes: an access pointidentifier 420, a current channel 422 graphical element, a directconflict indicator 427 graphical element, a near conflict indicator 428graphical element, an other signal indicator 429 graphical element, aproximity indicator 426 graphical element, and a recommended channel 423graphical element.

Each access point is represented in a list of access points by an accesspoint identifier 420. The access point identifier includes the name ofthe access point and, optionally, an icon indicating the type of accesspoint. Other information may also be displayed with the access pointidentifier 420. For example, a description of the physical location ofthe access point or notes describing special instructions when assigningchannels to a given access point. The current channel 422 indicates thecurrent channel being used by the corresponding access point.

The proximity indicator 426 includes a number of graphical elements thatclearly and quickly show the network administrator where there areproblems with interference between access points. A proximity indicator426 is shown for each access point. The proximity indicator 426indicates the detected signal strengths of the "I am here" messagesreceived at a given access point. The proximity indicator 426, in oneembodiment, is shown as a bar that is proportional to the detectedsignal strengths. The bar includes the direct conflict indicator 427,the near conflict indicator 428 and the other signals indicator 429. Thedirect conflict indicator 427 is proportional to the direct conflictvalue for an access point. The near conflict indicator 428 isproportional to the near conflict value for an access point. The othersignal indicator 429 is proportional to the other signal values for anaccess point. In one embodiment, the direct conflict indicator 427 isshown as red, the near conflict indicator 428 is shown as yellow, andthe other signal indicator 429 is shown as green. Thus, the networkadministrator can quickly see, by the amount of red showing, the presentconflicts between access points.

The recommended channel 423 indicates which channel the access pointshould be assigned to in order to reduce the amount of conflict. Thenetwork administrator can change these recommended channel assignments(see step 250), if so desired. When the network administrator selectsthe "apply" button, the network manager 110 sends the new channelassignments to the access points (see step 260).

Optionally, the process of FIG. 2 can be repeated to generate a newchannel assignment display 400 (after channel reassignment), as shown inFIG. 4. Note that the proximity indicator 426 now shows reducedconflicts. Alternatively, the channel assignment display 400 can berecalculated directly from the reduced conflict level table 372. In oneembodiment, a graphical element is included in the channel assignmentdisplay 400 to display a before and an after snapshot of a proposed setof channel assignments. In one embodiment, the channel assignmentdisplay 400, or some other graphical user interface, includes graphicalelements for selecting a set of unusable channels for a given accesspoint.

In one embodiment, the channel assignment display 400, or some othergraphical user interface, includes graphical elements for fixing aspecific access point on a specific channel. Thus, preventing the accesspoint to be assigned a different channel.

A method and apparatus for maintaining non-interfering frequencyassignments of wireless-based computer networking products has beendescribed. The access points detect their neighboring access points anda proposed set of new channel assignments is generated that eliminates,or reduces, the conflict between access points, without requiringassistance from the network administrator. The results of the neighbordetection is graphically displayed to allow the network administrator toeasily see the present status of the wireless network, given the presentallocation of channels. The network administrator can then modify theproposed set of channel assignments. Finally, the new channelassignments are sent to the access points.

What is claimed is:
 1. A method of assigning channels to a set of accesspoints coupled to a network, said set of access points including a firstaccess point and a second access point, said network including a set ofwireless network nodes, each access point communicates using one of saidchannels to a subset of wireless network nodes from said set of wirelessnetwork nodes, each channel corresponding to a different frequency rangein the electromagnetic spectrum, said method comprising:at least a firstaccess point of said set of access points transmitting a plurality ofmessages; determining a measure of interference between access pointscommunicating on a first channel from said plurality of messagesincludingtransmitting a first message from said first access point onsaid first channel, said first message indicating a presence of saidfirst access point, measuring a signal strength of said first message atsaid second access point, said signal strength corresponding to anamount of conflict between said first access point and said secondaccess point for said first channel, and transmitting a second messagefrom said second access point to said first access point, said secondmessage including a value corresponding to said signal strength and anidentifier, said identifier identifying said second access point as asource of said second message; determining a second set of channelassignments that results in a lower amount of interference betweenaccess points communicating on the first channel; and assigning saidsecond set of channel assignments to said set of access points.
 2. Themethod of claim 1 further including determining a measure of potentialinterference between access points communicating on two channels thatare near each other from said plurality of messages, where said twochannels are near each other when no other channel corresponds to arange of the electromagnetic spectrum between two ranges of theelectromagnetic spectrum corresponding to said two channels.
 3. Themethod of claim 1 further including determining a measure of an amountof jamming experienced by a one or more access points, said jammingresulting from a transmission by a source of electromagnetic radiationat a frequency corresponding to a channel.
 4. The method of claim 1wherein said second message is transmitted on said first channel.
 5. Themethod of claim 1 wherein said second message is transmitted on a wiredcommunications link between said first access point and said secondaccess point.
 6. The method of claim 1 wherein said first messageincludes a source address of said first access point.
 7. The method ofclaim 1 wherein said first access point communicates with a firstwireless network node on said first channel and wherein said firstmessage is transmitted at a greater signal strength than is a messagetransmitted from said first access point to said first wireless networknode.
 8. A method of assigning channels to a set of access pointscoupled to a network, said set of access points including a first accesspoint and a second access point, said network including a set ofwireless network nodes, each access point communicates using one of saidchannels to a subset of wireless network nodes from said set of wirelessnetwork nodes, each channel corresponding to a different frequency rangein the electromagnetic spectrum, said method comprising:at least a firstaccess point of said set of access points transmitting a plurality ofmessages; determining a measure of interference between access pointscommunicating on a first channel from said plurality of messagesincludingtransmitting a first message from said first access pointindicating a presence of said first access point, measuring a signalstrength of said first message at said second access point, said signalstrength corresponding to an amount of conflict between said firstaccess point and said second access point for said first channel;determining a second set of channel assignments that results in a loweramount of interference between access points communicating on the firstchannel; and assigning said second set of channel assignments to saidset of access points.
 9. The method of claim 8 further includinggenerating a conflict level table, said conflict level table including acommunications channel and a direct conflict value for each access pointin said set of access points, said communications channel indicating achannel on which a given access point is communicating, said directconflict value indicating a level of interference with access pointsother than said given access point communicating on said communicationschannel.
 10. The method of claim 9 wherein said direct conflict valuefor said given access point includes an total level of interference withaccess points other than said given access point.
 11. The method ofclaim 9 wherein said direct conflict value for said given access pointincludes a maximum level of interference with access points other thansaid given access point.
 12. The method of claim 8 wherein determiningsaid second set of channel assignments includes generating a second setof channel assignments that results in a reduced direct conflict valuefor a first access point in said set of access points.
 13. The method ofclaim 12 wherein determining said second set of channel assignmentsincludes generating said second set of channel assignments that resultsin a reduced direct conflict value for all of said access points in saidset of access points having a non-negligible direct conflict value. 14.The method of claim 1 wherein determining said second set of channelassignments includes generating said second set of channel assignmentsfrom a subset of said channels, said subset of said set of channelsexcluding a channel identified as not to be used for a given accesspoint.
 15. The method of claim 1 wherein said channels includes apreassigned channel for a first access point, and said second set ofchannel assignments includes said first access point being assigned tosaid preassigned channel.